In general, a permanent magnet forms a magnetic field at the periphery of the permanent magnet, and magnetically affects a magnetic material positioned in the magnetic field. However, since the magnetic flux caused by the permanent magnet is difficult to be controlled, alternative means such as an electromagnet have been used.
However, the electromagnet has problems in terms of stability because electric current needs to be consistently supplied to the electromagnet so as to generate magnetic force, and in a case in which the supply of electric current is suddenly shut off, magnetic force is eliminated, and as a result, a held magnetic material may be released. An expensive uninterruptible power supply (UPS) needs to be additionally added to an electromagnetic device in order to ensure stability. Therefore, the electromagnetic device consistently consumes electric current and needs to be equipped with the uninterruptible power supply to ensure stability, and as a result, there are problems in terms of production costs and maintenance costs.
Accordingly, the present applicant has developed devices which generate a magnetic field outside the device or eliminate the magnetic field by controlling magnetic flux from the permanent magnet, and have an effect on a magnetic material (see Patent Literature 1 to 3).
(Patent Literature 1)
Korean Patent No. 10-1319052B (Magnetic Substance Holding Device Using Permanent Magnet Energy Control)
(Patent Literature 2)
Korean Patent No. 10-1498864B (Magnetic Substance Holding Device)
(Patent Literature 3)
Korean Patent No. 10-1512610B (Magnetic Substance Holding Device)